[Venks]

Vykker resemblence- they are "Hermaphroditic self-impregnating masters of weird science" thus they all look the same due to constantly reusing the same DNA.
Also they are not completly the same take a single species of cat for example, to me all cats with orange fur look the same, but their is in fact subtle diffrences, if I really got to know these cats in time I would see diffrences.

Stranger's thoughts about Sekto- In that point in the game it was easy to tell Stranger didn't want anyone knowing about him, if he was intrested in working for him he would of actually tried looking for a Steef, do you remember Stranger kept saying he needed the operation for his life? Its becuase he had a huge bounty on his head becuase of Sekto, so of course he wanted to kill him.

Why Doc was by himself- This is merely my theory unlike the facts posted above but I believe this takes place after MO, sense Vykker's lab was blown up Vykkers would have to find other ways to make money resulting in Doc living all the way out here.